1. Field of the Invention
The invention relates to the field of apparatus for releasably attaching expendable stores such as a fuel tank to a vehicle and the like and, in particular, to an apparatus that is quickly resettable.
2. Description of Related Art
There are numerous approaches to releasably connecting expendable stores to a vehicle. For example, wing mounted gravity released weapons are attached to the wings of aircraft by means of bomb racks that incorporate retractable hooks that engage lugs on the weapon and uses external adjustable sway braces to prevent lateral motion. The hooks can be either electro-mechanically or explosively actuated. However such apparatus are limited to small expendables. The use of such an approach on a large external fuel tank mounted to a spacecraft would require massive external sway braces that would add significant weight to the spacecraft and increase drag to unacceptable levels.
On large external fuel tanks explosively actuated systems such as explosive bolts and the like have proven highly reliable, but require refurbishment after each use. In addition, during the installation of pyrotechnic devices, concurrent activities are severely restricted, increasing the overall "turnaround" time between launches. For example, U.S. Pat. No. 5,520,476 "Tie-Down And Release Mechanism For Spacecraft" by C. W. Marks, et al. discloses such an explosively actuated device. It includes a hollow housing mounted within the main body of the spacecraft having an internal lip at its end that abuts against an internal lip on a second hollow housing on the structure to be released. A segmented collet, having an external groove, is held in contact with the two lips such that they are retained within the groove. The collet in turn is held into contact with the lips by a toroidal spring supported by a movable cylinder. This cylinder includes a second groove positioned such that when the movable cylinder is actuated by the pyrotechnic charges, it drives the cylinder to a position where the spring can retract into the second groove thereon allowing the segmented collet to release the lips. Such explosively actuated systems can not be used on vehicles that require multiple dockings with another spacecraft because of the refurbishment requirement after each use. In the future, reusable booster spacecraft will require rapid turn around times and thus such vehicles must have only a minimum number of systems requiring refurbishment between launches.
U.S. Pat. No. 4,431,333 "Apparatus For Releasably Connecting First and Second Objects in Predetermined Space Relationship" by J. A. Chandler and U.S. Pat. No. 5,364,046 "Automatic Compliant Capture And Docking Mechanism For Spacecraft" by M. E. Dobbs, et al. disclose apparatus for connecting a spacecraft to another spacecraft. Here one of the vehicles includes an extendable probe having a bulb-like member at its end which engages a cone shaped funnel on the spacecraft. Upon the bulb like member bottoming in the funnel, a releasable detente secures the probe therewithin. Such systems, have the advantage of correcting for misalignment of the two vehicles during docking because the funnel tends to "capture" the probe. However, they are unusable for securing an expendable tank or the like to a launch vehicle. First of all, the need to accommodate misalignment is not required and the tank must be firmly secured to the booster in order to withstand the high aerodynamic and inertial G loads experienced by boosters. In addition, they do not provide means for adjusting the tension preload between the spacecraft nor are such systems retractable to a flush condition.
Thus, it is a primary object of the invention to provide an apparatus for releasably connecting first and second structures together, such as a reusable launch vehicle and an expendable external tank.
It is another primary object of the invention to provide an apparatus for releasably connecting first and second structures together that requires no refurbishment after operation.
It is a further object of the invention to provide an apparatus for releasably connecting first and second structures together that includes means to adjust the tension preload.
It is a still further object of the invention to provide an apparatus for releasably connecting first and second structures together that returns to a flush position within the external contour of the structure.